There is feature request logged in the Feedback
portal for extending the taxonomies items permissions, where you can vote for it. Note that most voted items are developed with higher priority.
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Sitefinity CMS Ideas&Feedback Portal
and vote to affect the priority of the items